1. Field of the Invention
The present invention relates to a motor compressor which is to be used in a cooling system of an air conditioner, refrigerator or the like.
2. Description of the Prior Art
Heretofore, motor compressors including a rotary compressor and a scroll compressor have been used in the cooling system of the air conditioner, refrigerator and the like.
This kind of compressor is shown in FIG. 1 of Japanese Patent Unexamined Publication No. 61-212689.
As shown in this drawing, within a closed container 101 are disposed a compression mechanism section 102 , a stator 104 and a rotor 105 which constitute a motor 103 , and a crankshaft 106 serving to transmit rotation of the motor 103 to the compression mechanism section 102 . Further, end plates of the closed container 101 are provided with a suction pipe 107 through which a low pressure refrigerant gas is to be sucked and a discharge pipe 108 through which a high pressure refrigerant gas is to be discharged.
With the above construction, as the rotor 105 constituting the motor 103 is rotated, rotation of this rotor 105 is transmitted through the crankshaft 106 to the compression mechanism section 102 . As the compression mechanism section 102 is rotated to perform the compressing function, a low pressure refrigerant gas sucked from the suction pipe 107 is compressed by the compression mechanism section 102 to become a high pressure refrigerant gas which is in turn released into the closed container 101 . Then, the high pressure refrigerant gas is passed through the space in the motor 103 and, after cooling the stator 104 and the rotor 105, discharged through the discharge pipe 108 to a refrigerating cycle (not shown).
However, in this kind of compressor, during an ordinary operation, in order to increase the compression efficiency by sealing the gap in the compression mechanism section 102 , oil is mixed in the refrigerant gas under compression. Further, within the closed container 101, lubricating oil is stirred by the rotor 105 of the motor so that a large number of drops of oil are scattered.
Therefore, since the high pressure refrigerant gas released from the compression mechanism section 102 into the closed container 101 is made to come into further contact with a large number of oil drops and catch the same here, a large quantity of oil is discharged through the discharge pipe 108 to the refrigerating cycle. Particularly, if the number of revolutions of the compressor is increased to increase the discharge of the refrigerant, the ratio of discharge of the oil (weight of oil to be discharged/weight of refrigerant to be discharged) is increased remarkably.
With the increase of the discharge of the oil from the compressor to the refrigerating cycle (as the ratio of discharge of the oil exceeds approx. 0.3%), not only is the pressure loss of the pipeline of the refrigerating cycle increased, but also the efficiency of heat exchange effected by the heat exchanger such as a condenser, an evaporator or the like is reduced, thereby giving rise to a problem that the refrigerating ability cannot be increased even if the number of revolutions of the compressor is increased or the factor of achievement of the refrigerating cycle is deteriorated.